A unified picture of the cosmic Dark Matter (DM) and Dark Energy (DE) has been one of the
key aspirations of modern researches within the standard paradigm of spatially flat
Friedmann-Robertson-Walker (FRW) cosmology
[1]}, [2]}, [3]}, [4]}, [5]}.
While there have been innumerable attempts to emulate the nature and properties of DM and DE,
a general consensus on the specific structure of the evolving dark sector remains elusive till
date. Although candidates abound, e.g. WIMPs and axions for the DM
[6]}, [7]}, [8]}, [9]}, [10]},
and a plethora of others for the DE (such as scalar fields, aerodynamic fluids and modified
gravitational artefacts)
[11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}, [21]}, [22]}, [23]}, [24]}, [25]}, [26]}, [27]}, [28]}, [29]}, [30]},
the emergent models have had their own pros and cons. One conundrum, of course, is the
`coincidence', i.e. the vast amount of fine-tuning required to set up the initial
conditions for the same order-of-magnitude contributions of DM and DE at the present epoch,
if they purportedly stem out of different fundamental sources. This is indeed perplexing,
given the strong observational support for the DE density to be closely akin to a cosmological
constant \(\Lambda \) , whereas almost the entire bulk of the DM to be `cold' and non-relativistic,
with energy density \(\rho ^{(c)}(t) \sim a^{-3} (t)\)  (where \(a(t)\)  is the cosmological scale factor,
and \(t\)  denotes the cosmic time coordinate).
